For many years the most popular means for supporting troughed conveyor belts has been through the use of a plurality of spaced-apart idler roller assemblies each comprising three or five rollers. Each of the rollers of each assembly is independently journaled at each end by bearings and is supported by an axle assembled on a common framework. The individual rollers are normally sloped upwardly and outwardly from the horizontally disposed centermost roller at an angle which may vary from 20.degree. to 45.degree. from the horizontal to provide the desired depth of trough. A difficulty generally experienced with three and five roller idlers is that the bearings and seals are located in each end of each roller and are exposed to moisture and contaminants which enter through the rotating bearing seals. In addition, the material utilized in the manufacture of three and five roller idlers is a ferrous material which is subject to rapid deterioration in corrosive environments.
Numerous attempts have been made to duplicate the troughing capabilities of multiple idler rollers by the use of a single catenary roller assembly. The structural means normally employed to support the idler roller assembly and the product conveyed is a wire rope cable or multiple cables to which rubber-like disks or wheels are bonded. The cable core permits deflection at the center of the assembly with the assembly being equipped with bearings at each end of the cable thereby permitting a rotation of the assembly about the curved catenary cable axis. The catenary configuration results from the natural sag of the assembly at its center due to its dead weight.
The primary problem with the utilization of such catenary idler rollers is the premature and often unanticipated failure of the cable core member. This failure results from the rapid rotation of the core member under tensile load while in a curved configuration thereby causing fatigue failure of the cable wire elements due to rapid reversal of stresses.
It is therefore a principal object of this invention to provide an idler roller which overcomes the tendency towards fatigue failure common to catenary idlers by employing a series of molded plastic idler wheels which turn in unison on a rigid curved axis rod.
A further object of the invention is to provide an idler roller assembly for a belt conveyor wherein the individual idler wheels are operatively interconnected so that they rotate in unison.
Yet another object of the invention is to provide an idler roller assembly for a belt conveyor comprising a plurality of idler wheels rotatably mounted on a curved rod with the idler wheels having a centrally disposed hub portion having a bore extending therethrough with the bore being tapered radially outwardly towards both ends from the center thereof.
Still another object of the invention is to provide an idler roller assembly for a belt conveyor which employs a plurality of individual idler wheels with the inner bearing surface of the idler wheels being formed from a bearing-like material providing lubricity to the rolling elements.
Yet another object of the invention is to provide an idler roller assembly for a belt conveyor including means for sealing the inner bearing surfaces from exterior contaminants.
Yet another object of the invention is to provide an idler roller which utilizes a molded plastic material which is wear resistant and which is impervious to deterioration from moisture or corrosive environments.
Still another object of the invention is to provide an idler roller assembly for a belt conveyor which is economical of manufacture, durable in use and refined in appearance.